1. Field of the Invention
The present invention relates to a composite substrate and a method for forming metal pattern.
2. Description of the Related Art
It is known that the formation of a desired metal pattern on a surface of a substrate by photolithography involves forming a resist pattern using a photoresist, forming a thin metal film layer on the surface on which the resist pattern is formed, and then removing the resist to form the desired metal pattern. This method is generally referred to as a lift-off process. For example, in a method for forming a thin metal film pattern described in Patent Document 1, after a resist pattern is formed on a substrate, a thin metal film layer is formed by sputtering. After immersion in a stripping solution for the resist pattern, an ultrasonic wave is applied to remove the resist pattern and an unnecessary portion of the thin metal film layer disposed on the resist pattern.
[Patent Documents]
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 07-300684 (paragraph [0004])
Also in a composite substrate in which a piezoelectric substrate is bonded to a supporting substrate with an organic adhesive layer interposed therebetween, a desired metal pattern may be formed by the lift-off process, as described in Patent Document 1. In the formation of a resist pattern by photolithography, a photoresist is applied to a surface of the piezoelectric substrate of the composite substrate, a photomask corresponding to a desired metal pattern is placed on the piezoelectric substrate, the photoresist is irradiated with light through the photomask, and development of the photoresist after removal of the photomask yields the resist pattern.